Non-invasive positive pressure ventilation (NIPPV) techniques, such as, for example, the application of continuous positive airway pressure (CPAP) have been used to treat sleep disorder breathing (SDB) such as obstructive sleep apnea (OSA) and other disorders such as chronic obstructive pulmonary disease (COPD) and congestive heart failure (CHF). Apparatuses for applying NIPPV techniques typically include a flow generator, including a blower, and a patient interface. A delivery conduit or hose is connected between the flow generator and the patient interface to deliver breathable gas at a positive pressure to the patient. A number of different patient interfaces are known and include, for example, nasal masks, nose and mouth masks, full-face masks, and nasal prongs and pillows. A headgear is typically utilized to position the patient interface on the patient's face and counterbalance the force of gravity and the force which results from the application of pressurized air which seeks to push the mask off the face.
NIPPV therapies are typically administered at night while the patient sleeps. In order for the therapy to be effective, the patient interface must be comfortable enough for the patient to remain sleeping, while maintaining a seal that is sufficient to deliver the breathable air at the required pressure.
Air leakage from between the patient's skin and the patient interface reduces the effectiveness of the therapy. Even very small leaks can be perceived by the patient and/or bed partner. The air leakage may cause the patient to increase the pressure of the mask against the patient's face. The air leakage may also cause the flow generator to increase the pressure of the delivered air, thus increasing the speed and noise of the flow generator. Increasing the pressure of the delivered air results in an increase in the flow of air, including the vent flow and leak flow. If a humidifier is used, the increase in the leak flow results in a waste of water from the humidifier. If supplemental oxygen is being provided to the flow of air, the increase in the leak flow causes a waste of some of the supplemental oxygen. Moreover, the air leakage may act as an irritant to the patient's eyes and disturb the patient's sleep.
Various masks have been proposed for minimizing leakage between the mask cushion and the face of the patient. Examples of these respiratory masks are disclosed in U.S. Patent Application Publication 2003/0029455, U.S. Pat. No. 6,418,928 and WO Patent Application Publication 2006/113321. Other approaches to minimizing leakage include attempting to provide a perfect seal between the patient's face and the patient interface. U.S. Pat. No. 6,834,650 is an example of such an attempt. WO Patent Application Publication 2006/102707 discloses a patient interface having a vacuum line as a return path from the patient interface. Leakage is prevented, but requires the use of non-vented patient interfaces.
There still exists a need for a patient interface that controls leakage and improves therapy for the patient by reducing, or eliminating, the main discomfiture associated with leakage.